Is there an easy way to make ie6/7 use a different style sheet
instead?

Yes, through conditional comments in the HTML [1]. However:
- it pollutes the HTML code
- it has unwanted side effects [2]
I did not test IE6. IMHO people/corporations that sill use it are
begging for troubles from HTML standard support up to security.

For reference, IE6 doesn't look half bad (for IE6). Rollover menus do

not show but the main links work fine. I think thats a nice example
of